D400 Anytime Soon?

I currently have a D200, but NAS is getting to me. I am looking at getting a D300, but if Nikon will be coming out with an upgrade camera (D400, for example) anytime soon, I would prefer to wait for the new model (for, say, no more than 6 months).

Any speculation as to when Nikon will have an upgrade model?

BTW, I do recognize that if one always waits for an upgrade camera to come out, one will never buy a new camera because something newer is always on the horizon. That said, waiting a few months, up to 6 months, is not a long wait.

Thanks

Mike